Aspect of Musashi

Reckless. At the start of its turn, the Aspect can gain advantage on all melee weapon attack rolls during that turn, but attack rolls against it have advantage until the start of its next turn.

Rage within. At the start of its turn, the Aspect must use its action to attack the nearest enemy creature to it. If no enemy creatures are nearby, the Aspect moves as close as possible to the nearest one.

Yin and Yang. The Aspect swaps body with the creature hosting it when this creature falls below one quarter of its health. The swap takes over fully the body of the host and lasts for 10 minutes. Any hits on the host's body can force the creature to roll a DC 18 Charisma saving throw, on a fail the host takes back full control of its body, at the same health he shifted. The swap can only occur once a day.

The Aspect of Musashi make two The Black Katana attacks or one Lashing step attack.

The Black Katana. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (1d10 + 4) slashing damage.

Expose the weakness. If a creature attempts a melee attack on the Aspect and misses, the Aspect can use its reaction to roll an attack roll against that creature.